V62SLASH12615-01XE-R datasheet(79/98 Pages) TI1

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SLLSEC6E – SEPTEMBER 2012 – REVISED JUNE 2019

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Application and Implementation

Table 6-4. Magnetics Requirements

PARAMETER

TYP

UNIT

CONDITION

Turn Ratio

1:1

—

±2%

Insertion Loss

–1

1 MHz to 100 MHz

Return Loss

–16

1 MHz to 30 MHz

–12

30 MHz to 60 MHz

–10

60 MHz to 80 MHz

Differential to Common Rejection Ratio

–30

1 MHz to 50 MHz

–20

50 MHz to 150 MHz

Crosstalk

–35

30 MHz

–30

60 MHz

Isolation

1500

Vrms

HPOT

6.2.2

Detailed Design Procedure

6.2.2.1

MAC Interface (MII/RMII)

The Media Independent Interface (MII) connects the PHYTER component to the Media Access Controller

(MAC). The MAC may in fact be a discrete device, integrated into a microprocessor, CPU or FPGA. On

the MII signals, the IEEE specification states the bus should be 68-Ω impedance. For space critical

designs, the PHYTER family of products also support Reduced MII (RMII). For additional information on

this mode of operation, refer to the AN-1405 DP83848 Single 10/100 Mbps Ethernet Transceiver Reduced

Media Independent Interface (RMII) Mode Application Report (SNLA076).

6.2.2.2

Termination Requirement

To reduce digital signal energy, 50-Ω series termination resistors are recommended for all MII output

signals (including RXCLK, TXCLK, and RX Data signals).

6.2.2.3

Recommended Maximum Trace Length

Although RMII and MII are synchronous bus architectures, there are a number of factors limiting signal

trace lengths. With a longer trace, the signal becomes more attenuated at the destination and thus more

susceptible to noise interference. Longer traces also act as antennas, and if run on the surface layer, can

increase EMI radiation. If a long trace is running near and adjacent to a noisy signal, the unwanted signals

could be coupled in as crosstalk. TI recommends keeping the signal trace lengths as short as possible.

Ideally, keep the traces under 6 inches. Trace length matching, to within 2 inches on the MII or RMII bus

is also recommended. Significant differences in the trace lengths can cause data timing issues. As with

any high-speed data signal, good design practices dictate that impedance should be maintained and stubs

should be avoided throughout the entire data path.

6.2.2.4

Calculating Impedance

Equation 2 through Equation 5 can be used to calculate the differential impedance of the board. For

microstrip traces, a solid ground plane is needed under the signal traces. The ground plane helps keep

the EMI localized and the trace impedance continuous. Because stripline traces are typically sandwiched

between the ground/supply planes, they have the advantage of lower EMI radiation and less noise

coupling. The trade off of using strip line is lower propagation speed.

Microstrip Impedance - Single-Ended:

(2)

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